Why is agreeing to help someone that you don't have the time, money or expertise to help a good thing? Isn't it extremely misleading to tell someone you'll help

Why is agreeing to help someone that you don't have the time, money or expertise to help a good thing? Isn't it extremely misleading to tell someone you'll help them when you can't deliver? Isn't it more responsible to direct that person to someone who does have the expertise to help? (edit: There's an assumption here that because one company can't help, that none can. Should we make this assumption?)